Applicable Systems
PLC
Symptoms
The PLC reports a DC bus undervoltage fault. The drive trips because the bus voltage dropped below the minimum operating level.
Possible Causes
- Input power supply voltage dip or momentary outage
- Power supply capacity insufficient for the drive load
- Loose or corroded power wiring connection causing voltage drop
Troubleshooting Steps
- Step 1: Measure the input supply voltage during operation with a power analyzer
Voltage remains stable within the rated range - Step 2: Tighten all power wiring connections at the drive terminals
All connections are tight with no voltage drop - Step 3: If power dips are frequent, install a voltage stabilizer or UPS
Supply voltage is stable and above the minimum
How to Reset
To reset: Restore the supply voltage to the rated range, then reset the fault.
Source: B&R Automation System Manual, B&R Industrial Automation
Category: PLC & VFD